Recently, attention has been given to methods for synthesizing a compound having a difluoromethylene group because the compound has a specific biological activity. The method in which a carbonyl group, a thiocarbonyl group or a thioacetal group is reacted with DAST (dimethyl amino sulfide trifluoride) for conversion into a difluoromethylene group (DAST method) and methods in which a halodifluoromethyl group is dehalogenated to provide a difluoromethylene group (e.g., Kumadaki method) are well known (Non-patent document 1).
However, the DAST method is provided at a high cost and has problems such as use of a reaction agent and a substrate which cannot be easily obtained or handled. The Kumadaki method also has problems such as high cost because of the necessity of 2 equivalents of copper atom as a catalyst for completion of reaction.